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Question
The bob A of a pendulum released from horizontal to the vertical hits another bob B of the same mass at rest on a table as shown in figure.
If the length of the pendulum is 1 m, calculate
- the height to which bob A will rise after collision.
- the speed with which bob B starts moving. Neglect the size of the bobs and assume the collision to be elastic.
Solution
a. Two balls have the same mass and the collision between them is elastic, therefore, ball A transfers its entire linear momentum to ball 8. Hence, ball A will come to rest after the collision and does not rise at all.
b. Speed with which bob B starts moving
= Speed with which bob A hits bob B
= `sqrt(2gh)`
= `sqrt(2 xx 9.8 xx 1)`
= `sqrt(19.6)`
= 4.42 m/s
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